1. Field of the Invention
This invention relates to a soldering flux.
2. Description of the Related Art
The great majority of soldering fluxes heretofore available comprise a rosin or rosin-modified resin supplemented with an activator consisting of an organic acid and a hydrohalic acid salt.
However, these fluxes leave residues on the substrate surface after completion of the soldering operation and may cause cracks on cyclic heating and cooling and tends to give false "rejects" in the incircuit test because of the failure of the contactor pin to penetrate down to the printed circuit of the board. Furthermore, on moisture absorption and temperature gain, these residues tend to cause corrosion of the base metal and deterioration of the electrical characteristics of printed circuit boards.
Therefore, it is common practice to perform cleaning with a chlorofluorohydrocarbon to remove residues of the flux after the soldering operation.
However, since the cleaning agent chlorofluorohydrocarbons are under rigorous environmental control today, cleaning with them is now a virtually forbidden procedure.